1. Field of the Invention
The present invention relates to an additive for anti fouling paint, and in particular relates to an additive for antifouling paints which makes it possible to prevent marine organisms and marine algae from adhering the bottom of ships made of various materials including steel ships, FRP (fiber reinforced plastic) ships and wooden ships, submerged structures, various fishing nets including aquaculture nets, buoys, and industrial water system facilities.
2. Description of the Prior Art
In the prior art, an antifouling paint containing rosin or organic tin has been painted onto ships, submerged structures, fishing nets and the like in order to stop corrosion and drag due the adhesion of marine organisms such as barnacles, mytilus coruscus, algae and the like. Further, an antifouling paint containing rosin or organic tin has also been applied to aquaculture nets in order to prevent the destruction of marine products due to the adhesion of various marine organisms.
In this connection, ships cruising the ocean face the problem of damage due the adhesion of marine organisms on the ship bottom. Further, because the carpet-like layer of algae and shellfish adhering to all parts of the ship below the ocean surface, including the ship bottom, creates a huge drag force, a variety of adverse effects occur. For example, at an output of 80%, a ship having absolutely no adhered bodies will have a cruising speed of 10 knots, but the same ship having a large amount of adhered bodies will only have a cruising speed of 5.about.6 knots. Consequently, the greater output required of ships having a large amount of adhered bodies places a huge stress on the engine, and over time this can damage the engine. In particular, because a cruising ship will experience a large drag force due to the adhesion of marine organisms on ships, there will be (1) an increase in the negative load placed on the engine, (2) an increase in fuel consumption, and (3) damage to the ship itself.
In order to counter such damage, the bottom and sides of ships are painted with a special paint. This paint has a slippery surface like that of eel skin, and this property makes it difficult for bodies to adhere to such painted areas. In particular, in recent years the progress of research development in the field of paints has produced a paint that slowly dissolves over time (hydrolysis type paint) and a paint that slowly wears away over time (a self-abrasion type paint), but even these special paints are not able to sufficiently eliminate the adhesion of bodies such as oyster shells, algae and ulva. Moreover, surface painted with such paints must be repainted before the paint dissolves or wears away. Furthermore, in addition to containing paint components (e.g., organic tin) which are highly toxic to marine life, such paints form one cause of ocean pollution. For these reasons, the use of these special types of paints is not preferred.
Further, repainting is required due to the peeling off and wearing away of paint on ships and the like, and in the case of a small ship, repainting must be carried out once every 3.about.6 months, while in the case of a large ship such as a 100m-class ship, repainting must be carried out once a year. In this regard, when ships are to be repainted, the adhered bodies must first be removed, and then after surface soil and salt has been washed away, the step of repainting is carried out, and for a large ship the step of removing adhered bodies can itself be an arduous task, with all steps requiring about one week to complete.
It is not an exaggeration to say that the world economy is supported by the flow of goods transported by ships from various countries. In this connection, painting is an absolute requirement for any and all ships, whether they be tankers, freighters or passenger ships, and all ships are faced with the problem of bodies such as oyster shells, algae and the like adhering to their hulls.
The painting of ships addresses the problems caused when organisms living in the ocean adhere and grow on the hulls of ships, namely, lowering of speed due to increased drag, increased fuel consumption, greater engine loads, shorter engine life, and rapid damage to the hull due to increased hull vibration. The main cause of these serious problems is the adherence of marine organisms such as oyster shells, algae, ulva and the like, and in order to reduce such adherence, the following products have tested. Namely, a (1) self-abrasion type paint and (2) ahydrolysis type paint have been tested.
(1) Self-Abrasion Type Paint
By utilizing the driving force of the ship, self-abrasion type paint is designed to peel away and fall off, with adhered bodies such as oyster shells, algae and ulva falling off together with the paint that falls off, and one example of a self-abrasion type paint is a paint which uses a copolymer containing organic silicon.
However, in the case where self-abrasion type paint is applied to wooden ships or the like, the lack of a flat bottom means there are grooves where it is difficult for the paint to peel away, and this makes it impossible to prevent the adhesion of organisms such as oyster shells, algae, ulva and the like.
(2) Hydrolysis Type Paint
Hydrolysis type paints are designed to be hydrolyzed by sea water (i.e., salt water), with an organic tin compound or the like being eluted as the paint vehicle dissolves in sea water, and as this antifouling agent is eluted, organisms such as oyster shells, algae, ulva and the like fall off into the ocean together with such paint compounds.
However, while hydrolysis type paint can be painted onto FRP ships, it can not be used for aluminum ships because of the hazardous compounds created by chemical reactions between the paint and aluminum. Further, because hydrolysis type paints utilize reactions with seawater (i.e., salt water), they are not effective in lakes or rivers (i.e., in fresh water).
Moreover, because the (1) self-abrasion type paint will peel away and the (2) hydrolysis type paint has components that will wash away, both paints (1) and (2) have a relatively short binding period of approximately 6 months. In response to this, various paint manufacturers have expended a great deal of effort in developing ways to prevent as much as possible the adhesion of organisms and ways to extend the binding period of paints, but no effective solutions have been found yet.